Most of the time we use Simulink to simulate a PID controller. But this files run it as a Matlab code.
Extract the files to the working directory and just run the file PID_ctrl_call.m.
You can vary the PID tuning parameters in the file pid_ctrl.m and see what will happen.

Thanks for an interesting submission. If you are interested in designing and tuning PID controllers in MATLAB and Simulink, please take a look at new PID tuning capabilities shipped in Simulink Control Design in R2009b:
http://www.mathworks.com/products/simcontrol/description2.html

There is also a webinar on the subject:
http://www.mathworks.com/company/events/webinars/wbnr38619.html?id=38619&p1=636028070&p2=636028082